In general, a wheel rim is fastened to a wheel hub by a plurality of fasteners, such as bolts and nuts. Currently, the fastener head raised above the wheel rim can be generally categorized into two types. The first type has a hexagonal cross sectional head, and can be fastened or unfastened by tools like hex wrenches and hexagon sockets. The second type has specially-shaped head that can only be fastened or unfastened using specially designed tools, thus having anti-theft effects.
However, once the above fasteners are loosened, they can be easily unfastened. Thus, there is a need to further improve the anti-theft effects.